1. Field of the Invention
The present invention relates to semiconductor light emitting devices, and more particularly, to a semiconductor light emitting device including a light emitting element.
2. Description of the Background Art
In general semiconductor light emitting devices employed as the illumination device of a camera, the backlight of a liquid crystal display device, and the like, much current is conducted to achieve higher luminosity. However, a large current flow to the semiconductor light emitting device will cause increase of the temperature of the light emitting element per se, leading to poor light emitting efficiency to degrade the light emitting element in the worst case.
Therefore, measures to release the heat generated at the light emitting element outside efficiently in order to lower the temperature of the light emitting element have been adopted. One such measure is to increase the area or the thickness of the lead frame to which the light emitting element is die-bonded. Another known measure is to replace the material around the light emitting element with a material of high heat conductance.
In order to achieve high luminosity in the semiconductor light emitting device, the method of directing the light emitted from a light emitting element to a specified direction is employed. A resin lens or a reflector is attached to direct light towards the specified direction.
Additionally, a semiconductor light emitting device having the aforementioned measures combined is proposed to emit light of higher luminosity towards a specified direction. By way of example, one such semiconductor light emitting device disclosed in Japanese Patent Laying-Open No. 2003-115615 will be described hereinafter. Referring to FIG. 15, a light emitting element 103 and a reflector 105 are provided on the surface of a substrate 101. Two leads 104a and 104b of light emitting element 103 is soldered 107 to the wiring of substrate 101. A predetermined resin 109 is provided at the region of leads 104a and 104b and the region of reflector 105.
In this semiconductor light emitting device, leads 104a and 104b are brought into direct contact with resin 109 to achieve heat dissipation by allowing the heat generated at light emitting element 103 to be conducted to reflector 105 via resin 109.
Additionally, Japanese Patent Laying-Open Nos. 2002-176203 and 2003-197974 disclose a semiconductor light emitting device that achieves heat dissipation by conducting the heat generated at a light emitting element to a reflector via resin having high heat conductivity. The semiconductor light emitting device disclosed in Japanese Patent Laying-Open No. 2002-176203 has the reflector formed integrally with the lead to allow direct conduction of heat generated at the light emitting element to the reflector without the intervention of resin and the like.
The semiconductor light emitting devices set forth above had the following problems. If the heat generated at the light emitting element is to be conducted to a reflector via resin, the resin must be cured with the reflector fixed at a predetermined location with respect to the substrate and the light emitting element so as to achieve fixation between the reflector and the substrate. Therefore, a dedicated jig to position the reflector at predetermined site was required since heat conduction cannot be achieved efficiently if the position of the reflector is deviated. Furthermore, it was necessary to control the amount of resin during the fixation of the reflector so that the resin does not flow excessively to a region where resin is not required. In the case where the reflector and lead are formed integrally, the semiconductor light emitting device will have the reflector covered with mold resin since the reflector and lead are formed integrally from the beginning. Thus, there was the problem that heat cannot be released efficiently to the air from the reflector.